Draft means for furnaces



July 7, 1942. R. F. CARROLL DRAFT MEANS FOR FURNACES Filed July 19, 1940 INVENTOR. d

- ATTORNEY.

BY f 8 Patented July 7, 1942 UNITED STATES PATEL??? Oi FliCE DRAFT MEANS FOR FURNACES Robert'F. Carroll, Duluth, Minn.

Application July 19, 1940, Serial-No. 346,399

3 Claims.

This invention relates to draft regulating means for furnaces,v and has special reference to such a device for use in connection with mechanically stoked furnaces.

The principal object of the invention is to provide more simple and practical means for automatically furnishing natural draft to a stoker fed furnace, when the forced draft from the stoker mechanism ceases, the advantages of which are well known, to avoid burning out of the grates, etc.

Another object of the invention is to provide such means whereby the condition of the fire within the furnace may be conveniently observed, or access had thereto through said means.

Other objects and advantages of the invention will appear in the following description thereof.

Referring now to the accompanying drawing, forming part of this application, and wherein like reference characters indicate like parts:

Figure l is a broken section and elevation of the fire box of a furnace and side elevation of a stoker associated therewith.

Figure 2 is a broken plan view of Figure 1.

Figure 3 is an enlarged sectional view on the line 33, Figure 1.

Figure 4 is a front elevation of Figure 3.

i represents the fire box of a furnace or other type of heating plant and 2 represents the mechanical stoker for feeding fuel to such a furnace which is usually provided with the air conduit 3 for passage of air from the fan 4, driven as by the electric motor 5; all of which are common in stokers of the type illustrated.

It is also known to be old to provide a drop damper within the conduit 3 intermediate of its ends, and which damper may be so constructed as to fall by gravity and thereby permit air from the outside atmosphere to pass through the conduit 3 to the chamber I2 below the furnace grates when the forced draft from the fan 4 ceases, and there are many objections to such form of admitting natural draft to the conduit when desired.

My present invention contemplates the use of a laterally disposed chamber, such as illustrated at 6, positioned at the extreme innermost terminus of the conduit 3, and through which air from the outside atmosphere may be conveniently conducted to the chamber I 2, transverse the longitudinal axis of the conduit 3; the principal object of such specific location of the chamber 6 being that access to the chamber I2 of the furnace may be thereby readily had therethrough. The outer end of the chamber 6 is open as at 9,

and within said chamber, close to said open end 9, is installed a vertically swingable damper, illustrated at l, the same being hinged as at 8'to the top of the chamber. The opening 9 is approximately the entire cross sectional area of the outer end ofthe ch-amber, therebeingbut a relatively short vertical wall ll acrossthe bottom of the opening 9 sot-hat when the damper is swung towards the outer end of the chamber 6 it will strike the wall H and thus effectively close the otherwise open end of the chamber and prevent air passing therethrough. This damper, of course, will remain in closed position as long as the fan 4 is in operation, as the pressure therefrom within the furnace will bear against the inner surface of the damper and hold it closed. When, however, the fan 4 is stopped by the action of thermostats or otherwise, the pressure within the furnace ceases, and due to the chimney draft there is caused a partial vacuum within the chamber I2, which, if not relieved, will re sult in extreme heat therein, often causing burning of the grates and other damage to the heating plant. As is obvious, however, when this partial vacuum within the chamber [2 occurs, the damper I will be drawn inwardly, thereby admitting air from the surrounding atmosphere through the opening 9 into the conduit 3 and to the chamber 12, transverse the extreme innermost end of the conduit.

If the pressure on opposite sides of the damper 'l were equal, of course, the damper would hang vertically, and it is evident that the swinging closure 1, pivotally suspended as at 8 from the top of the compartment 6, functions as an exceedingly sensitive means, most readily affected by the presence or absence of forced draft within the conduit 3 and adequately insures against overheating or burning of the grates of the heating plant.

It may be desired that some natural draft be admitted through the opening 9, and therefore I have provided an auxiliary damper indicated at l3, which, in this instance, is a circular one, being manually rotatable upon its central pivotal support l4 and provided with the catch indicated at l5 extending from the lower circumferential edge thereof for overlapping engagement of the wall II, when the auxiliary damper is closed, as illustrated in Fig. 4. This damper is provided with a plurality of circular openings indicated at I5 which may be made to register with similarly shaped openings indicated at I! in the damper 1, or so turned as to close same entirely, when the damper l is closed, if

so desired, thus providing for any desired permanent draft when the damper 1 is otherwise closed.

It is to be noted that this auxiliary damper, being carried upon the outer face of the damper 1, will, when the auxiliary damper is not functioning as holding means, by its weight insure the damper remaining at all times slightly open, when, for example, the pressures are substantially equal on opposite sides of the closure.

Having thus described my invention, what I claim and desire to secure by Letters Patent, is:

l. The combination with the air conduit from a mechanical stoker to a cooperative furnace, of a compartment having an opening provided with a closure, adjacent the furnace end of said conduit and communicating directly with said furnace whereby to provide both access and air from the surrounding atmosphere therethrough to said furnace, and a manually controlled damper on said closure whereby a limited amount of air may be allowed to pass therethrough irrespective of the pressures on either side thereof and means carried by said damper to optionally hold said closure closed.

I 2. The combination with the air conduit from a mechanical stoker to a furnace fed thereby, of means for the conduct of natural draft to said conduit, said means comprising an opening in said conduit, a pivotally mounted closure therefor, and means for causing said closure to remain slightly open when pressures are substantially equal upon opposite sides of said closure, and a manually controlled damper on said closure whereby a limited amount of air may be allowed to pass therethrough irrespective of the pressures on either side thereof and means carried by said damper to optionally hold said closure closed.

3. The combination with the air conduit from a mechanical stoker to a furnace fed thereby, of means for the conduct of natural draft to said conduit, said means comprising an opening in said conduit, a closure pivotally mounted from the upper edge of said opening, said closure being held closed when the air pressure within the furnace is greater than atmospheric and opened with said air pressure within the furnace is less than atmospheric, and a manually controlled damper on said closure whereby a limited amount of air may be allowed to pass therethrough irrespective of the pressures on either side thereof. and means carried by said damper to optionally hold said, closure closed.

ROBERT F. CARROLL. 

